I'm also trying to teach my kids the idea of files and how everything on the computer are pretty much all files.
Interesting. As a generation that grew up on Windows, that's probably my mental model as well. Keeping specific files like music, videos, photos organized and sharing them on pen-drives was a big thing even 10 years ago - and to an extent, this is completely gone. Can you expand why you want to teach that?
Files have metadata that describes to the operating system what they are for, and how they are to be used.
Etc, etc.
This is information that I think will be very enlightening for them, even though not strictly required to operate a computer these days.
It's more generous to assume that the OP is asking what tools they should consider to support, rather than replace, their parental duties.
It is a good model, but it depends on the age of the kid too. More mature kids will follow through, but all of them, including adults, will need help when the attack is strong from online companies.
Beyond that, I will look for the good replies on this post - I am leaning towards "big hammer" blocking and allowing/curating sites/videos. The Internet is a big place.